1. Field
Embodiments of the invention relate to a clutch controlling apparatus for a vehicle, and, more particularly, to a clutch controlling apparatus for a vehicle which can allow smooth start of the vehicle even if the engine speed has a dispersion arising from various conditions of the engine when a start map control is entered after a start permission decision.
2. Description of the Related Art
Previously, an automatic clutch controlling apparatus which can carry out start of a vehicle smoothly has been attempted. For example, Japanese Patent Laid-Open No. 2007-139120 proposes an automatic clutch controlling apparatus which can learn a clutch transmission torque characteristic which is used for clutch control upon starting. Meanwhile, Japanese Patent Laid-Open No. 2006-336853 proposes a clutch controlling apparatus which can carry out appropriate fastening force control for target torque regardless of drop of the coefficient of friction of a starter clutch or increase of the clearance between plates.
The clutch controlling apparatuses disclosed in Japanese Patent Laid-Open No. 2007-139120 and Japanese Patent Laid-Open No. 2006-336853 can cope with a case in which the clutch stroke amount varies by deterioration of a clutch apparatus or the like. However, these clutch controlling apparatuses fail to pay attention to the fact that an appropriate clutch-torque capacity of a starter clutch requires correction when a difference appears between an engine speed at a point of time of start permission decision and a current engine speed upon clutch connection.
For example, when a start permission decision is made and a start map control is entered, a dispersion appears in the engine speed depending upon various conditions of the engine. For example, where start permission conditions that the throttle opening is greater than 1 degree and the engine speed is higher than 1,200 rpm are set, since the engine speed corresponding to the throttle opening of 1 degree differs among different engines, start of the engine may be permitted at the engine speed of 1,200 rpm, or start of the engine may be permitted at 1,400 rpm. A start map sets the clutch-torque capacity using at least the engine speed as a parameter, and as the engine speed increases, a higher clutch-torque capacity is required. Therefore, a difference in start feeling appears depending upon the engine speed.
Initially, it is desirable that an engine starts with torque of a similar level if the throttle valve opens by a similar degree. However, since a start capacity of a clutch corresponding to an engine speed is read in from the start map, a clutch-torque capacity that differs depending upon a difference of the engine speed upon a start permission is read in, and this gives rise to a difference in feeling of starting when the clutch is connected.
Particularly in fast idle, since the engine speed is high with respect to the throttle opening, if the throttle valve opening becomes large during fast idle and start is permitted, then a large clutch-torque capacity corresponding to the high engine speed during the fast idle is read. Therefore, since the clutch-torque capacity with which high torque transmission is carried out is set with respect to the degree of throttle opening operation, the start torque may become different from that experienced by the driver.
The object of some embodiments of the present invention resides in provision of a clutch controlling apparatus for a vehicle which can correct, when start permission conditions are satisfied, the value of the clutch-torque capacity with respect to the engine speed to enhance the start feeling.